The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
In a satellite-based positioning system, a satellite positioning receiver receives broadcasted satellite navigation messages from multiple satellites detectable by the receiver and determines an estimated position of the receiver with respect to the broadcasting satellites based on the received satellite navigation messages. An indicator of the sensitivity of satellite positioning receiver is the Time-to-First-Fix (TTFF). The TTFF measures how long it takes a receiver being activated to first output of an estimated position under a variety of conditions. In some applications, a significant portion of TTFF is spent in acquiring the satellite signals by the receiver's radio frequency section, and an additional time is spent in decoding the navigation message portion of the satellite signal to extract satellite navigation information (i.e., satellite position and clock state information) by the digital section. In many applications, the environmental conditions may limit the sensitivity of a satellite positioning receiver. For example, in limited sky-view conditions where the satellite signals are weak or in a twinkle, the satellite positioning receiver, due to the relationship between data error rate and signal carrier to noise ratio (CNR), is hard to correctly decode the navigation message portion of the satellite signal so the receiver is difficult of determining which satellites to search for, thereby increasing total processing time substantially.